Brad Pitt’s children are expected to spend Father’s Day with their mom, Angelina Jolie, RadarOnline.com has learned. The shocking development comes after 18-year-old daughter Shiloh legally dropped her dad’s last name on her birthday in May, following in her 19-year-old sister Zahara’s footsteps, who announced herself at a sorority ceremony as Zahara Jolie. Despite sharing six children, including Shiloh, with Angelina, Brad will reportedly be spending Father’s Day all alone. According to sources close to the situation, Shiloh, Zahara and their siblings — Maddox, 22, Pax, 20, and 15-year-old tw…